1. Field of the Invention
The present invention relates generally to vapor and gas delivery systems and, more particularly, to the heating of a gas line body feedthrough used in a vapor delivery system such as a chemical vapor deposition chamber or an atomic layer deposition chamber.
2. State of the Art
Modern semiconductor processing equipment, specifically chemical vapor deposition (CVD) and atomic layer deposition (ALD) systems, are migrating to the use of organometallic precursors such as tantalum tetraethoxide dimethylamino ethoxide (TAT-DMAE) as well as halogen-metallic chemistries such as TiCl4 and others for metal, metal-oxide and metal-nitride film depositions (collectively referred to herein as organometallic precursors). Conventional precursors have typically been delivered in a gas or vapor state thus making them amenable for use in the vapor deposition process, including ease of maintaining the precursors in the vapor state, as they are delivered to the chamber from the vapor source. However, organometallic precursors are typically delivered for use as a liquid and sometimes as a solid. Many of such precursors have low vapor pressures and others exhibit moderate vapor pressures. The organometallic sources are typically vaporized and transported through the delivery plumbing to the process chamber. Conventional methods of vaporization include the use of bubbler ampoules or direct liquid injection systems, which comprise a chemical ampoule, a liquid flow meter, a heated injector, a carrier gas mass flow controller (MFC) and heated vapor delivery lines between the precursor source and the chamber.
Referring to FIG. 1, a conventional CVD chamber 100 is shown. The chamber 100 includes a body 102 and a lid 104 which are configured to allow removal of the lid 104 from the body 102. The removable lid 104 provides for access to and maintenance of the chamber interior including the chamber cavity 106. A vapor delivery path 107 is conventionally defined to pass through the chamber body 102 using a feedthrough device 108 which connects to the heated vapor plumbing (conduit) 110 at the lower side of the chamber at one end 112 thereof and mates to the lid 104 at the opposite end 114. The vapor delivery path 107 may continue through additional vapor plumbing (conduit) 116 before it travels through the lid 104 and is discharged into the chamber cavity 106 through a vapor delivery head 118, also termed a “showerhead” due to its physical configuration. The vapor is then discharged through the vapor delivery head 118 and is deposited on a semiconductor substrate 120 such as a silicon wafer. The semiconductor substrate 120 is positioned on a susceptor unit 122 during the deposition process as is understood by those of ordinary skill in the art.
One problem with the above described deposition chamber 100 is that the chamber body 102 is maintained at a temperature which is lower than that of the heated vapor plumbing 110. For example, the heated vapor plumbing 110 may be maintained at a temperature of approximately 140 to 160° C. while the chamber body 102 is maintained at a temperature of approximately 45 to 65° C. The reduced temperature of the chamber body 102 causes, through heat transfer, the temperature of feedthrough device 108 to also be lower than that of the heated vapor plumbing 110. The temperature differential between the feedthrough device 108 and the heated vapor plumbing 110 may cause condensation to occur within the vapor delivery path 107 as the vapor passes through the feedthrough 108. Newly utilized organometallic precursors are particularly susceptible to such condensation due to their relatively low vapor pressures.
The occurrence of condensation within the feedthrough 108 may negatively impact the chemical vapor deposition process in various ways. For example, the condensation may result in particulate contaminants flowing through the vapor delivery path 107 and being deposited on the surface of the substrate or wafer 120. Introduction of such particulates ultimately results in a defective semiconductor wafer or other substrate 120 which is unsuited for use in subsequent semiconductor packaging processes.
Additionally, the condensation may cause clogging or material build-up within the feedthrough device 108 as well as in the vapor plumbing 116 positioned downstream therefrom along the vapor delivery path 107. Such clogging may have a deleterious effect on the flow characteristics of the vapor passing therethrough. Additionally, material build-up may have a corrosive effect on the feedthrough device 108 and vapor plumbing 116.
While it is possible to route the heated vapor plumbing 110 around the chamber body 102 such that it connects directly through the lid 104 to the vapor delivery head 118 (thereby eliminating the feedthrough device 108 and additional vapor plumbing 116), in order to provide continual heat to the flowing vapor along the vapor delivery path 107, such a configuration is undesirable for various reasons.
For example, removal of the lid 104 from the chamber body 102 would require mechanical disconnection of the heated vapor plumbing 110. This would increase the amount of time required to service and maintain the CVD chamber 100. Perhaps even more significantly, mechanical disconnection of the heated vapor plumbing 110 would increase the potential for contamination the CVD process and the products produced thereby. Such increased potential for contamination results from the fact that the CVD chamber 100 is conventionally located and operated in a plenum 124 adjacent a clean room (not shown) which may be separated by a barrier 126 from a mechanical room 128. Wafers 120 are passed from the adjacent clean room into the CVD chamber 100 for processing. The implementation of a heated vapor line running exterior to the chamber body 102 in the plenum 124 would require increased maintenance activities within the plenum area 124 resulting in the increased likelihood of particulates and contaminants entering the plenum area 124, or possibly even into the adjacent clean room, each time repair or maintenance is required.
Additionally, the repeated connection and disconnection of the heated gas plumbing (i.e., from the lid 104) leads to the degradation of the mechanical connection. For example, a conventional mechanical connection used in chemical delivery systems includes a VCR® metal gasket face seal fitting. The VCR® fitting provides for the compression of a metal (or sometimes polymer) gasket between two opposing toroid surfaces. After repeated compression (i.e., resulting from repeated disconnection and connection of the piping) the toroid surfaces will flatten out and ultimately fail to seal. This necessitates costly replacement of the fitting and may possibly require the fabrication and welding of new piping hardware.
In view of the shortcomings in the art, it would be advantageous to provide a deposition chamber which allowed for the use of organometallic precursors having relatively low vapor pressures without condensation of such organometallic precursors occurring during delivery of the vapor to the chamber.
It would also be advantageous to provide a method of modifying existing deposition chambers to allow the use of organometallic precursors therewith. Particularly, it would be advantageous to provide a method of converting a chemical vapor deposition chamber configured for use with conventional precursors into an atomic layer deposition chamber or a chemical vapor deposition chamber suited for use with organometallic precursors.